{
"ErrorPattern": [
"SendAsync_Success_ConnectionSetupActivityGraphRecorded",
"Unexpected EOF trying to read request header"
],
"BuildRetry": true,
"ExcludeConsoleLog": false
}System.AggregateException: One or more errors occurred. (Sequence contains no matching element) (Unexpected EOF trying to read request header)
---> System.InvalidOperationException: Sequence contains no matching element
at System.Linq.Enumerable.Single[TSource](IEnumerable`1 source, Func`2 predicate)
at System.Net.Http.Functional.Tests.DiagnosticsTest.<>c__DisplayClass17_0.<SendAsync_Success_ConnectionSetupActivityGraphRecorded>b__1(Uri uri)
...
---> (Inner Exception #1) System.IO.IOException: Unexpected EOF trying to read request header
at System.Net.Test.Common.LoopbackServer.Connection.ReadRequestHeaderBytesAsync()
at System.Net.Test.Common.LoopbackServer.Connection.ReadRequestDataAsync(Boolean readBody)
at System.Net.Http.Functional.Tests.DiagnosticsTest.<>c.<SendAsync_Success_ConnectionSetupActivityGraphRecorded>b__17_7(GenericLoopbackConnection connection)
The pattern is intentionally scoped (test method name + LoopbackServer EOF line, AND-matched in order) to avoid over-matching unrelated tests that also use LoopbackServer.ReadRequestHeaderBytesAsync and legitimately drop the client connection (cancellation, retry, connection-limit tests, etc.).
Build
https://dev.azure.com/dnceng-public/public/_build/results?buildId=1477557
Build leg reported
Build Libraries Test Run release coreclr windows x86 Release
Pull Request
#129727
Known issue core information
Fill out the known issue JSON section by following the step by step documentation on how to create a known issue
{ "ErrorPattern": [ "SendAsync_Success_ConnectionSetupActivityGraphRecorded", "Unexpected EOF trying to read request header" ], "BuildRetry": true, "ExcludeConsoleLog": false }Additional information about the issue reported
Sibling of dotnet/dnceng#5922.
Same loopback-server race in
System.Net.Http.Functional.Tests.SocketsHttpHandler_DiagnosticsTest_*.SendAsync_Success_ConnectionSetupActivityGraphRecorded, but the HTTP/2 path surfaces a different inner exception than the HTTP/1.1 path, so the existingErrorMessage-based matcher on #5922 only catches the Http11 variant.Observed failure (PR #129727, build 1477557, Windows x86 Release):
Affected test variants on the reported build:
SocketsHttpHandler_DiagnosticsTest_Http2.SendAsync_Success_ConnectionSetupActivityGraphRecorded(useTls: False)SocketsHttpHandler_DiagnosticsTest_Http2.SendAsync_Success_ConnectionSetupActivityGraphRecorded(useTls: True)The pattern is intentionally scoped (test method name + LoopbackServer EOF line, AND-matched in order) to avoid over-matching unrelated tests that also use
LoopbackServer.ReadRequestHeaderBytesAsyncand legitimately drop the client connection (cancellation, retry, connection-limit tests, etc.).Note
This issue was filed with assistance from GitHub Copilot.
Known issue validation
Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1477557
Error message validated:
[SendAsync_Success_ConnectionSetupActivityGraphRecorded Unexpected EOF trying to read request header]Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 6/23/2026 9:32:19 PM UTC
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